Splodge
We have a similar problem at the local airport, but luckily its not the manager. When the person does overstep the mark, we make a written report, ask for the tapes to be pulled and the person is disciplined, not that it has much effect on them, unfortunately. Everyone on the airfield knows who the person is and groans when they are on duty - they are not even competent as a controller. The person's behaviour is putting people off visiting this airport, which must in the long run, affect business for the FBO's and restaurants, etc.
Squibbler - this is not something I ever came across in the UK, but assuming that Splodge is using a different airport to the one I fly out of, that is the third controller I've heard of who is abusive (two of those I have heard myself) in the USA. And by abusive, I don't mean "having a bad day", I mean directly insulting the pilots over the radio, regularly bawling people out over the radio, questioning pilots knowledge of their own airplanes etc, etc. All stuff that if someone said it to you sitting in a bar, you'd probably thump them (verbally or physically) and leave - not really ideal practice on the radio. Its not a case of "throwing your toys out of the pram" - when all the other controllers are people I would consider friends, but one is a prize jerk, there's no reason to start throwing toys around.
Good Luck!